Detecting Soil Contaminants

Biosensors for groundwater monitoring.

Imagine you are sitting in a room by a window on a sunny afternoon in September.
You start to feel warm and you want to know the temperature in the room, so
you bottle a sample of the air and mail it to a laboratory in another part of
the country. Several weeks later, on a snowy October morning, you receive a
report telling you what the temperature in the room was on that warm September
afternoon. Sound absurd? Sure it does. But this is actually the way most environmental
chemical analysis is conducted, bringing the researcher a single, time-delayed
measurement that may not accurately reflect the current situation.

Colorado State University chemical engineering Professor Ken Reardon thinks
there is a better way. He puts it like this: If you want to know the temperature
in the room, you look at a thermometer on the wall  so why not something
similar for analysis of groundwater?

Reardon is applying this concept of in situ (in place) continuous measurement
to his work in monitoring groundwater for agricultural pesticides. Currently,
the primary method for measuring pesticide contamination is to remove a groundwater
sample from a well, package it in several sample vials, ship it to a lab to
be analyzed by gas or liquid chromatography, and receive the analysis weeks
later. Reardon would like to replace laboratory analysis of groundwater with
reliable, easy-to-use field sampling methods that produce real-time results.

Reardon and his research team -graduate students Neema Das and Brinson Willis
and collaborators Linda Henk, research assistant professor of chemical engineering,
and Reagan Waskom, Colorado Extension specialist in soil and crop sciences 
are developing unique bio-sensors to detect the presence of agricultural pesticides
in groundwater. In a biosensor, a biological component, such as enzymes or whole
cells, is fused to the end of a transducer, such as an electrode or optical
fiber. When a contaminant is detected by the biosensor, the transducer takes
the chemical signal from the biological component and turns it into an electronic
signal that can be continuously monitored.

"Continuous groundwater monitoring at the site of pesticide production
and use is important for detecting spills and tracking the effectiveness of
clean up efforts," Reardon explains. "It's also important from the
application end in helping farmers to apply just the amount of pesticide they
need and to know where it is going after they put it on their fields. "

So far, Reardon and his colleagues have developed fiber optic biosensors capable
of detecting certain chlorinated organic compounds, such as atrazine, at levels
as low as one part per billion. No other similar device for inexpensive, continuous,
compoundspecific sensing has ever been developed, and Reardon has been issued
a provisional patent for his sensor design.

While the developments on this project are very promising, Reardon says the
next challenge is to discover appropriate detection systems for additional chemical
contaminants.

"What we've got is a start," he says. "What we've found out
about pesticides and atrazine we hope to apply to any form of groundwater contamination.
The goal of our current research is to make our instruments more effective in
analyzing different classes of chemicals. Right now we are working on developing
sensors for two other chemicals -alachlor and metalochlor -but obviously there
are hundreds more. "

The ultimate goal of Reardon's research is to enable greater agricultural productivity
with less environmental impact. While his biosensors may not help us replace
the use of pesticides in agriculture, they will ensure that pesticides are used
more safely and responsibly. And as companies develop new pesticides that are
more environmentally friendly, Reardon and his team will continue to develop
more sensors to detect them.